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Saturday, August 10, 2013

The Story of Ants – Biology and Behaviour, Implications for Control

I have recently been giving some talks on pests and diseases in the home and garden and how to solve problems.

I thought it might be useful to publish some of the notes from these talks. This first one is about ants. I have summarised the biology and behavior of ants and what the implications of these are on how to control infestations.

Nuptials

Flying ants (not all species) are ants mating

Queens and males mate in flight

After mating males die and queens fly to seek nest (not usually more than 100m from original nest)

Queen looses wings

Starts colony

Flying ants annoy people as there can be many thousands. Treatment is not usually effective and most of the ants will die within a day or two.
To prevent infestation it may be advisable to treat possible nest sites in area with spray (NO Bugs Super, NO Ants) and use granules (Ant Sand and Lawngard Prills).
Nest Site

Dry – rain could drown nest

Warm – insects are more active when warm

Sunny – radiant heat can make ground and ants warm even on days with cool air temp – micro-climate

Sandy soil – easy to dig out nest chambers, well draining

E.g. under concrete path, under rock etc.

Sometimes nest in building, but if so, it probably be in exterior wall or eaves on sunny side

New nest genetically similar or the same as old nest – co-operation – same colony – super colony

NZ imported species spread from one or few original colonies – all genetically similar and will co-operate – may be one huge colony (super colony)

Important not to disturb nest (particularly one with multiple queens) as disturbance causes queens and workers to bud; heading off in different directions to set up new nests; he result being spread of the problem. I.e. do not spray nest site before baiting for ~2 weeks first. When spraying or using granules at nest site treat around nest entrance/s not in nest entrances.
It is likely that other nests are in the vicinity. Controlling/killing one nest is rarely enough to get rid of them permanently. Ants are likely to spread in again from a neighbouring nest/colony.
Multi-queen colonies/nests

Some species will have more than 1 queen in a nest (e.g. Argentine Ants, Darwin Ants)

Thousands, tens of thousands, even hundreds of thousands in single nest

Super colony – many millions?

~5-10% foraging workers – so what are seen is small part of colony

Killing all the workers (foragers) that are seen in a garden or house will not kill the colony. Nest can reproduce and replace 5-10% in a few days. Baits are most effective as the poison is taken back to the nest to kill at/in the nest. Use sprays and granules as barriers to nuisance trails.
Feeding

Protein – insects, seeds…..

Needed for colony growth and producing larvae

Some species target other insects and invertebrates that compete with them for food; removing competition (Argentine ants when moving into new area, biodiversity threat)

Foraging workers follow trail like ‘robots’ and may walk past and ignore other food

Each time a forager returns with food it also adds to chemical trail, encouraging more workers to follow it to food

As food runs out trail diminishes and fewer workers follow it until it stops

Ants live in a ‘chemical world’ and can be attracted to or repelled by some chemicals including cleaners, insecticides etc.

Baits must be placed on clean places with no deterrent chemicals. Do not spray areas around baits. Use sprays as barriers.
Baits may be ignored for days when ants are feeding somewhere else or the colony needs a different food type. Do not move baits, even if they are not being fed on. But replace bait as it is eaten and if it gets dried hard.

Collected food fed to other workers, queens and larvae in nest that do not go foraging

Direct feeding – food carried by foragers and passed straight on to others

For some ants (e.g. white footed ant) bait toxins are not easily passed on to others in a colony as the ant has ingested the poison and died, or the toxin is filtered out of production of anal secretion or sterile eggs.

Species

Almost all species that are pests have come in from overseas (invasive).

Identification of ant species can be important in knowing how to treat most effectively.

Colony Death

No queens – in super colony species a queen can be recruited from another nest

No food

Nest drowned out

Cold

A combination of control methods is almost always required to get rid of an ant infestation. Pro-active control each year is the best method.
Ants outside in the garden are rarely a problem, only when they trail indoors do they become a pest. Therefore, treat to keep ants outside and prevent their entry.What is the world's largest ant? The Eleph ant.